As an agricultural planter row unit travels across fields with variable soil types, soil moisture, residue levels and topography, it is difficult to maintain a constant depth of fertilizer and/or seed due to the changing conditions. This problem is complicated by the fact that the optimum pressure for any given soil condition can be different for different implements carried by the same row unit. For example, hard soil might require increasing the down pressure of the soil-opening implement more than the down pressure of residue-clearing devices and closing implements carried on the same row unit. On the other hand, farming with higher residue levels may require greater increases in the down pressures for the row-clearing devices than for the opening and closing implements.
As computers and GPS systems have allowed crop production to be managed in a location-specific way as an implement moves through a field, it has become necessary to achieve more rapid changes in the setting or adjustment of the various implements.